Recent 'NBTI' studies have come to involve very high electric fields, yet these same studies are used to criticize the lower field 'NBTI' models. This study examines both high- and low-field degradation phenomena by monitoring the initial threshold voltage shift (VTH) as a function of stress time and stress voltage. We demonstrate that the initial VTH is recoverable and decays rapidly as the stress voltage is reduced. We also monitor the transient transconductance (GM) degradation which surprisingly indicates the presence of an electron trapping/de-trapping component. We argue that the initial VTH and GM degradation behaviors are consistent with high-field stress degradation. The electron trapping component of the 'recoverable' degradation is unexpected and must be addressed to insure accurate NBTI lifetime predictions.
Proceedings Title: IEEE International Reliability Physics Symposium Proceedings
Conference Dates: April 27-May 1, 2008
Conference Location: Phoenix, AZ
Conference Title: International Reliability Physics Symposium
Pub Type: Conferences
NBTI, High-Field Stress, hole-trapping, electron-trapping